Russian seamen line up on an unidentified submarine believed to be an Akula-class submarine during a military parade training in Vladivostok in this July 25, 2008 file photo. (Xinhua/Reuters, File Photo) Photo Gallery>>>

    BEIJING, Nov. 10 -- An accident on board a Russian submarine has left at least 20 sailors dead and sent 21 others to hospital.

    As the brand-new nuclear submarine was being tested in the Sea of Japan, its fire safety system was accidentally turned on.

    The system released freon gas causing asphyxiation among the crew. A probe will focus on what activated the fire-fighting system, as well as possible violations of operating procedures.

    Navy officials say a siren warning the crew that the fire-extinguishing system was turned on may also have failed. The sub is now back at its base on Russia's Pacific coast.

    (Source: cctv.com)